The subject invention relates generally to watthour meters for measuring electrical consumption by utility customers and, specifically to an optical and associated signal processing technique for the operation thereof.
The escalating cost of electricity and opposition thereto on the part of the public and public service commissions has motivated electric utilities to seek novel and resourceful means for minimizing their capital investment as well as to foster energy conservation. One of these means entails the adoption of a communication system to permit remote monitoring of the individual customer loads for rate application purposes as well as remotely controlling the loads in order to curtail same in the event of an emergency or to smooth out the peak demand load curve. In order to remotely monitor electric consumption by a customer, the meter reading must be converted to an equivalent electrical analog for transmission back to the central monitoring site. Although many of the earlier communication systems employ some mechanical arrangement for performing the foregoing electrical signal conversion, some systems such as described in U.S. Pat. No. 3,943,498 perform the conversion directly from the meter rotor rotation rather than from the meter dial reading. The light reflecting technique employed in the foregoing patent, whereby light reflections from the meter rotor using some reflective rotor pattern are used to monitor the rotor rotation and consequently electric consumption through an electrical analog thereof, is suitable for new meter units which can be designed to accommodate the photoelectric detection circuitry that is made a part thereof. However, such would not be the case in retrofitting the millions of existing meters that would have to be modified or replaced in inaugurating a monitoring and control communications system.
Fiber optic techniques for optically transmitting information have found many applications, including remote data reading as delineated in another U.S. Pat. No. 3,806,875. However, the attenuation of the light in the course of transmission, particularly when the light is initially generated from a low power source, for example to minimize cost and miximize lifetime, renders it especially difficult for the light reflection detecting circuitry to recognize genuine electrical analogs in the presence of spurious signals produced by noise and varying ambient temperatures which change component characteristics. Therefore, notwithstanding these prior uses for fiber optic transmission techniques, it is believed that the subject invention affords a unique combination with many notable advantages for adapting existing meters for operation in a monitoring and control communications system.
With the foregoing in mind, it is a primary object of the present invention to provide a new and improved means for remotely monitoring the rotation of a watthour meter rotor to produce an electrical analog of the electric consumption.
It is a further object of the present invention to provide such a new and improved rotation monitoring means through the use of fiber optic techniques which facilitate the adaptation of existing meters for use in modern monitoring and control communications systems.
It is still a further object of the present invention to provide such a rotation monitoring means which entails signal processing techniques for minimizing the adverse effects of noise and varying ambient temperatures and which affords digital implementation to promote cost effectiveness.
The foregoing objects as well as others and the means by which they are achieved through the present invention may be best appreciated by referring to the Detailed Description of the Invention which follows hereinafter together with the appended drawings.